The present invention relates to a device for determination of the steering angle in a motor vehicle and, more particularly, to a device for determination of the steering angle in a motor vehicle with a steering column, a steering mechanism and a steering tie rod, wherein the device comprises a first means for generating a fine signal according to the angular position of the steering wheel, a second means for generating a coarse signal according to the number of revolutions through which the steering column has been turned in one or the other direction and means for coupling or combining the fine signal and the coarse signal to obtain the steering angle.
The actual steering wheel position is required for safety reasons immediately after operation of the ignition switch for certain safety systems in a motor vehicle, e.g. for the vehicle dynamic control. In motor vehicles equipped in this way steering wheel angular position sensors operating as absolute sensors are required, which allow a definite determination of the angular position immediately after turning on. A steering wheel angular position sensor is known, for example, from International Patent Application PCT/DE 95/00343.
This known sensor for determination of the steering wheel angular position of the motor vehicle has a first code disk, that is detected by a first plurality of receivers or sensors and which rotates with the same speed as the steering wheel. A second code disk rotates with a quarter of the speed as the first code disk and has three code tracks that are detected by a second plurality of sensors. In an associated microcontroller the so-called fine signal is derived from the output signal of the sensors associated with the first code disk, while the second sensors supply the coarse signal, since the fine signal repeats itself after an angular rotation of .+-.720.degree., also 1440.degree.. An accurate determination of the steering angle can be performed by a suitable coupling or combining of the fine and coarse signals.
Also code disks which have cavities forming the actual code are used in the known sensor for determination of the steering wheel angle. Hall barrier devices that each cooperate with a magnet are used as sensors. The Hall barrier devices are located on one side of the code disk, while the magnets are located on the other side of the code disk. Thus the code disk acts as a diaphragm and the Hall barrier devices produce output signals that detect whether or not a cavity of the code disk is located between the Hall barrier device and the associated magnet.
The known arrangement for detection of the steering angle in the motor vehicle is very expensive, especially in its manufacture and construction. If the coarse signal is derived from a gear controlled by the steering column, then tolerances very strongly effect the precision of the measured steering angle. Furthermore a suitable driving torque is required for this arrangement.